The invention is directed to a machanism for guiding and advancing a sheet material. It is particularly applicable for, although not necessarily limited to, the feeding and guiding of fabrics, and for purposes of illustration the invention will be described in the context of a device for feeding and guiding of fabrics.
In the processing of fabrics into garments, there is a wide variety of operations that require the simultaneous advancement and positioning of the fabric. Perhaps the most common such operation is in the hemming of the fabric along its edges. In order to perform this type of operation, as well as many others, with any degree of automation, it is necessary to be able to sense the position of the fabric edge as the fabric is advanced, and to manipulate the fabric laterally, while it is being advanced, in order to maintain the fabric edge in a predetermined alignment. Many devices have been proposed in the prior art for this general purpose. Such prior devices have not, however, been altogether satisfactory for one or more reasons of excessive cost, inadequate performance, excessive size, lack of reliability, etc. The present invention is directed to a uniquely simple, compact, low cost mechanism which engages the fabric surface and is functional to drive the fabric simultaneously in each of the two principal rectilinear axes, thus serving to advance the fabric longitudinally while effecting any necessary lateral adjustment of the fabric edge.
In accordance with the invention, a drive mechanism is provided which comprises a plurality of spherically contoured drive elemtents, which are arranged to drivingly engage one surface of a fabric or other sheet material to be controlled and which are driven controllably to advance the material in a longitudinal direction. Uniquely, the spherically contoured drive elements are mounted to be bodily rotated about an axis extending in the longitudinal or material advancing direction. Means are provided for controllably rotating the spherical drive elements about said longitudinal axis simultaneously with the forward-driving rotation of the drive elements. The arrangement is such that the spherically contoured drive elements serve to drive the fabric forwardly or rearwardly, in response to rotation of the drive elements about their principal rotational axes, while the material is driven laterally, in one direction or the other, by bodily rotation of the drive elements about said longitudinal axis.
In one of its simplest forms, the mechanism of the invention comprises a pair of spherically contoured, rotatable drive elements, which are mounted in a rotatable frame structure. The rotatable frame structure is supported for rotation about a longitudinal axis, in relation to the direction of material movement. The two spherically contoured drive elements are mounted for rotation about axes at right angles to the longitudinal axis of rotation of the frame structure. In addition, where two drive elements are employed, their respective axes of rotation are oriented at 90.degree. with respect to each other. If more than two drive elements are utilized, their respective axes of rotation are displaced angularly in a uniform manner according to the number of drive elements (e.g., three drive elements would have their axes displaced at 60.degree.).
Pursuant to another aspect of the invention, the orientation and dimensioning of the spherically contoured drive elements is such that, in any rotary position of the rotatable frame structure, at least one of the spherically contoured drive elements will be in driving contact with the material to be manipulated. Thus, in a mechanism utilizing two such driving elements, the spherically contoured surface of a drive element, in the plane of its rotational axis, will subtend and angle of at least about 90.degree. from the center of the sphere, located symmetrically with respect to the axis of rotation of the drive element. Thus, each drive element is in the form of a sphere, mounted on a shaft for rotation about the axis of that shaft and truncated at its opposite "poles". The extent of truncation of these spherically contoured drive elements must be sufficient to enable rotational mounting thereof from within the confines of the projected spherical contour. At the same time, the maximum extent of truncation is limited by the requirement that in any rotary position of the mounting frame, at least one drive element will have surface contact with the material to be manipulated.
In accordance with another aspect of the invention, a unique form of drive mechanism is provided for the spherically contoured drive elements such that the speed of rotation of the drive elements is varied automatically with any change in the effective radius of the surface portion of a drive element actually engaging the material to be manipulated. In this respect, as the spherically contoured driving elements are rotated about the longitudinal axis of their supporting frame, in order to manipulate the material laterally, the radius of the surface areas of the drive elements having operative contact with the material will vary from a maximum, at the center of the spherically contoured element engages the fabric, to a minimum, where the spherical element engages the fabric near the truncated side of the element. Since the effective radius of the spherical element with respect to is own axis of rotation decreases toward the "poles", it is necessary to correspondingly increase the speed of rotation of the drive element in order to maintain a uniform forward advancing speed. In the mechanism of the invention. this is accomplished by driving the spherically contoured driving elements through the medium of a moving flexible belt, having a working section which is parallel to the plane of the material to be manipulated and which is driven in a direction opposite to the direction of longitudinal advancement of the material but at the desired speed of such advancement. The working section of the belt engages the spherically contoured drive elements in a surface area which is directly opposite the area in which the drive elements engage the material itself. Accordingly, the drive belt will at all times engage the spherically contoured elements at the same effective radius as the material to be manipulated. Exclusive of any slippage, the material to be manipulated will thus have the same forward speed as the working section of the belt, even though the rotational speed of the spherically contoured drive elements may vary in accordance with the rotational positioning of those drive elements about the longitudinal axis of the supporting frame.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of a preferred embodiment, and to the accompanying drawings.